The present invention relates to a plunger pump, and more particularly to a plunger pump suitable for supplying solution or liquid by the extrusion action of the plunger within a pump chamber.
In a liquid chromatograph, solution is supplied at a high pressure by using a plunger pump. The supply of solution is carried out by the extrusion action of a plunger of the pump. In the use of the pump, a small amount of solution adheres to a peripheral wall of the plunger and leaks out of the pump chamber through a sliding contact seal portion of seal member with the plunger as the plunger is reciprocated. A problem of conventional systems resides in the fact that solid material precipitated from the leaking solution damages the seal member. In order to cope with this problem, in, for example, Japanese Patent Unexamined Publication 58-165581 corresponding to European Patent Publication No. 0095,448A1, an apparatus is proposed wherein, as shown in FIG. 8, an annular clearance 104 is formed around a plunger 101, with the annular clearance 104 being sealed between seal members 102 and 103. A cleaning liquid 106 is introduced into the clearance 104 through a channel 105, whereby the precipitated solid material is removed from the plunger 101.
Since the annular clearance 104 around the plunger 101 is narrow and a distance between the cleaning solution channel 105 and the seal member 105 is long, it is difficult to generate a sufficient cleaning liquid flow through the clearance 104 to clean the clearance 104. In addition, in the conventional apparatus, since the cleaning liquid 106 is supplied from a liquid reservoir 109 through a conduit 110, pump line 111 and conduit 112 to the channel 105, and is further discharged through a conduit 113 to a liquid reservoir 114, it is not possible to observe or detect leakage of liquid from the pump chamber 108, formed in the pump housing 107, due to a degradation of the seal member 102. Since it is not possible to observe or confirm the damage or degradation of the seal member 102, it is not possible to know a suitable time for replacement of the seal member 102.